Sc(OTf)3/BF3•OEt2-Catalyzed Annulation of 3-Formylchromones with Functionalized Alkenes: Access to Diverse 2-Hydroxybenzophenones

The Sc(OTf)(3)/BF3 center dot OEt2-catalyzed annulation of 3-formylchromones with functionalized alkenes for the direct construction of 2-hydroxybenzophenones is described. Sc(OTf)(3)/BF3 center dot OEt2 acts as a synergistic catalyst, providing rapid synthetic access to diversely and highly functionalized 2-hydroxybenzophenones. This reaction has excellent regio- and chemoselectivities and is suitable for late-stage functionalization. The reaction proceeds via [3 + 3] and [4 + 2] cycloaddition processes, through carbonylene, Diels-Alder, or aldol-type reactions. Furthermore, this protocol tolerates the various functional groups present in natural terpenes and steroids.

Automated summary

This study describes the Sc(OTf)(3)/BF3 center dot OEt2-catalyzed annulation of 3-formylchromones with functionalized alkenes, providing a direct synthetic route to 2-hydroxybenzophenones. The reaction exhibits excellent regio- and chemoselectivities, suitable for late-stage functionalization. Additionally, it proceeds via [3 + 3] and [4 + 2] cycloaddition processes, tolerating various functional groups found in natural terpenes and steroids.